I wouldn't compare eyes with a lense.
"One recent photography book I was browsing through repeated the oft-made claim that a 50mm lens most closely matches that which our eyes see, the so-called "normal" lens. The first problem with this, of course, is that everyone's eyes are a little bit different. More to the point, the eye/brain connection includes a number of subtle features, such as peripheral vision and near-constant reorienting and focusing. In general, I find that I "see" about a 24mm-equivalent field of view, with my vision concentrated on the equivalent of anything from a 80mm to 300mm lens (and this range has narrowed as I grow older). (For those that are curious, most human eyes are about 16mm in focal length and the pupil's iris can manage effective apertures of from about f/2 to f/11.)"
If using a 50mm on full frame for a head shot, filling the frame, you will be pretty close to your camera and will have a lot of perspective distortion (big nose, tiny ears). Another option is to have some distance but then crop the image, but that will give you lower quality. An 85mm or even longer would be a better choice for any head shot.
And a funny thing I found out about how our brain can adapt to the signals from our eyes.
"Psychologist George M. Stratton conducted, in the 1890s, experiments in which he tested the theory of perceptual adaptation.[2] In one experiment, he wore a reversing glasses for 21½ hours over three days, with no change in his vision. After removing the glasses, "normal vision was restored instantaneously and without any disturbance in the natural appearance or position of objects."[2]
On a later experiment, Stratton wore the glasses for eight whole days. By day four, the images seen through the instrument were still upside down. However, on day five, images appeared upright until he concentrated on them; then they became inverted again. By having to concentrate on his vision to turn it upside down again, especially when he knew images were hitting his retinas in the opposite orientation as normal, Stratton deduced his brain had reprocessed his vision and adapted to the changes in vision."